GFP expression in murine alveolar macrophages in vitro. Shown is fluorescence microscopy of adherent alveolar marophages 48 hours after infection with AdGFP at various moi. Infection with AdNull is used as control. GFP fluorescence is shown in green. Nuclei are counterstained with DAPI (blue). Autofluorescent intracellular infections appear yellow-orange. (A) AdNull, 200 moi. (B) AdGFP, 10 moi. (C) AdGFP, 50 moi. (D) AdGFP, 200 moi. Bar = 50 μm.